This invention relates to a device for measuring of the concentration of a component, e.g., glucose, of a complex medium, e.g., blood of a patient.
Devices for measuring of the concentration of glucose in blood are known through, inter alia, U.S. Pat. No. 4,229,542. Similar devices are described also in U.S. Pat. Nos. 4,123,353 and 4,266,021, and in British Pat. No. 1,564,788. The measuring procedure with these known devices comprises an initial calibration step, in which the measuring unit is calibrated against a standard solution (calibration solution) containing the component, e.g., glucose, in a known concentration. Thereafter, the concentration of the component in the complex medium is performed. For further information concerning this measuring procedure, reference is made to any of the above-mentioned patents.
A drawback with this known measuring procedure is that calibration is performable only at the beginning of each measurement. This means that after an initial calibration one must rely upon this calibration result during the whole measurement of the concentration of the component from the complex medium. This is of course undesirable, since the measuring unit (particularly, if it is a measuring electrode) easily can give rise to systematic deviations during the measurement depending on, for example, temperature disturbances or the like. It would be desirable to be able to perform calibration intermittently also during the measuring procedure in order to achieve a check of the accuracy of the measuring unit and thereby a safer measuring result.